After every <B>RRDp::cmdB> you have to issue an <B>RRDp::readB> command to get
<B>RRDtoolB>s answer to your command. The answer is returned as a pointer,
in order to speed things up. If the last command did not return any
data, <B>RRDp::readB> will return an undefined variable.

If you import the PERFORMANCE variables into your namespace,
you can access RRDtools internal performance measurements.

read RRDtools response to your command. Note that the $answer variable will
only contain a pointer to the returned data. The reason for this is, that
RRDtool can potentially return quite excessive amounts of data
and we dont want to copy this around in memory. So when you want to
access the contents of $answer you have to use $$answer which dereferences
the variable.

these variables will contain totals of the user time, system time and
real time as seen by RRDtool. User time is the time RRDtool is
running, System time is the time spend in system calls and real time
is the total time RRDtool has been running.

The difference between user + system and real is the time spent
waiting for things like the hard disk and new input from the perl
script.

If you set the variable $RRDp::error_mode to the value catch before you run RRDp::read a potential
ERROR message will not cause the program to abort but will be returned in this variable. If no error
occurs the variable will be empty.